Cemented ferrochrome material

ABSTRACT

There is described a cemented ferrochrome material including from 15% to 99% of ferrochrome and from 1% to 85% of a metallic binder. The material is made by mixing or milling together particles of ferrochrome and the binder metal until the particle size of the mixture is substantially less than 325 mesh, compacting and heating to a temperature within the range of 1850*-2400*F. The product has excellent corrosion resistance, high hardness, good strength and is highly impermeable to liquids. It may be used in any applications in which such properties are desirable, such as ball pen balls, wear pads and mounts adapted to be adhered to materials having compatible coefficients of thermal expansion.

[ 1 Aug. 26, 1975 0 United States atent Hill [ CEMENTED FERROCHROME MATERIAL [75] lnventor: Franklin J. Hill, Janesville, Wis.

[73] Assignee: The Parker Pen Company,

Janesville, Wis.

[22] Filed: May 28, 1974 [21] Appl. No.: 473,817

Related U.S. Application Data [63] Continuation of Scr. No. 302.418. Oct. 31 1972, abandoned. which is a continuation-in-part of Scr. No. 107,804. Jan. 19, 1971. Pat. No. 3,708,283, which is a continuation-in-part of Scr. No. 14,527 Feb. 26, 1970, abandoned.

[52] U.S. Cl. 29/182; 29/1822; 29/1827; 75/200; 75/201; 75/203 [51] Int. Cl. B22F l/00 [58] Field of Search.... 2 /182, 182.2, 182.5. 182.7; 75/201, 203, 200

[56] References Cited UNITED STATES PATENTS 2.370.396 2/1945 Cordiano 75/214 3,628,921 12/1971 Hill 75/204 Primary ExaminerBenjamin R. Padgett Assistant ExaminerB. Hunt [57] ABSTRACT There is described a cemented ferrochrome material including from 15% to 99% 0f ferrochrome and from 1% to 85% of a metallic binder. The material is made by mixing or milling together particles of ferrochrome and the binder metal until the particle size of the mixture is substantially less than 325 mesh, compacting and heating to a temperature within the range of 18502400F. The product has excellent corrosion resistance, high hardness, good strength and is highly impermeable to liquids. It may be used in any applications in which such properties are desirable, such as ball pen balls, wear pads and mounts adapted to be adhered to materials having compatible coefficients of I thermal expansion.

22 Claims, N0 Drawings CEMENTED FERROCHROME MATERIAL CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of application Ser. No. 302.418.fi1ed Oct. 31. 1972 and now abandoned. which is in turn a continuation-in-part of application Ser. No. l07.804.fi1ed Jan. 19. 1971 and now U.S. Pat. No. 3.708.283. which in turn is a continuation-in-part of application Ser. No. 14.527.fi1ed Feb. 26. 1970 and now abandoned.

The present invention relates to a cemented ferrochrome material having particularly advantageous properties and to a powder metallurgy process for pre paring the same.

It has been proposed to make stainless steels by powder metallurgy wherein relatively minor amounts of a ferrochrome powder were included as an alloying ingredient. Examples of such prior art materials and processes are to be found in the U.S. Pat. Nos. of Kalischer U.S. Pat. No. 2.333.573. Cordiano U.S. Pat. No. 2.370.396 and Carlson et al. U.S. Pat. No. 2.827.407.

It is the object of the present invention to provide a cemented ferrochrome material in the form of a composite mass in which particles of ferrochrome retain their individual indentity and are bound together by a metallic binder having a melting point lower than that of the ferrochrome.

lt is another object of the invention to provide a ccmented ferrochrome material characterized by excellent corrosion resistance. high hardness and good strength.

Another object of the invention is to provide a cemented ferrochrome material of low porosity with a resulting high impermeability.

A further object of the invention is to provide a cemented ferrochrome material having a low coefficient of thermal expansion.

Another and further object otthe invention is to provide a cemented ferrochrome material which is of low cost as compared to other powder metal products with similar corrosion resistant properties.

A still further object of the invention is to provide a novel process for preparing a cemented ferrochrome material having the advantageous properties set forth above.

Other objects of the invention will become apparent from the following detailed description.

The product of the invention comprises a composite mass of finely divided ferrochrome particles cemented together by a binder metal or alloy having a melting point lower than that of the ferrochrome. The product may contain from 1571 to 9971 by weight of ferrochrome and from 17! to 8571 by weight of binder. but it is preferred that the ferrochrome be present in an amount between about 257: and 9571 by weight. As the percentage of ferrochrome is decreased. the hardness decreases. but the strength and toughness are increased. Accordingly. a balance will be struck in accordance with the particular use to which a given product is to be put.

As will be seen hereinafter. temperatures are employed in the making of the product which are above the melting point ofthe binder and at the sintering temperatures of the ferrochrome. Accordingly. particles of ferrochrome will be sintered at their points of contact. There will be very little contact between particles of 2 ferrochrome in products which are high in binder and proportionately more in products which are high in forrochrome.

The metallic binder substantially completely fills all of the spaces between particles 01 ferrochrome. The product can be made to have an extremely low porosity and thus is to all practical purposes impermeable to liquids of every description. It is to be stressed that the ferrochrome to a large extent maintains its separate identity so that the product is a composite one. although some alloying may take place and the smaller ferrochrome particles may dissolve. at least partially. in the liquid binder.

The size of the ferrochrome particles is quite important. They should have a distribution ranging from less than 1 micron to 50 microns. Particularly good products are those in which the ferrochrome particles prior to being subjected to sintering temperature during fabrication were of a size such that 9071 by weight would pass through a 325 mesh screen. A very satisfactory product is one in which 99% by weight of the ferrochrome particles are of a size less than 20 microns.

The ferrochrome of the material according to the invention should contain from about 60% to by weight ofchromium. from about 25% to 4071 by weight of iron and from about 0.1% to 77! carbon. There can be used any of the ferrochromes commercially available as an alloying ingredient. these ferrochromes being sold in particulate form. although not in the finely divided form desired in the present products. Both high carbon and low carbon ferrochromes. as well as one containing silicon. may be used in making the present products. but a high carbon ferrochrome is preferred.

A particularly preferred high carbon ferrochrome is one containing about 7071 by weight of chromium. 25% by weight ofiron. and 5% by weight of carbon. The following is atypical screen analysis in weight "/1 ofa commercial ferrochrome of this description:

A large number of metals and alloys can be employed as the binder in the instant cemented ferrochrome materials. it only being required that the metal or alloy have a melting point lower than that of the ferrochrome. Iron, nickel and cobalt metals and their alloys are quite suitable for use as binders and as alloys there may be mentioned nickel-copper. nickel-manganesecopper and cobalt-nickel-chromium. Silver and its alloys with palladium and with palladium and manganese also form suitable binders.

A particularly preferred series of binders are those described in my patent. US. Pat. No. 3.628.921. comprising binder alloy compositions containing by weight. about 30 to 60% cobalt. 20 to 50% nickel. 18 to 20% chromium. 0.1 to 1% platinum and to 3% iron. Especially preferred binder alloy compositions contain by weight about 45 to 55% cobalt. 25 to 35% nickel. 18 to 20% chromium. 0.5 to 17: platinum and 0% iron. Other platinum containing binders can be used as well. Thus the binder can be an alloy ol'platinum with iron. nickel. cobalt. chromium. manganese. copper. silver. palladium. and their alloys with each other. and other met als. ln certain cases. some of the binder alloy constituents necessary for forming the liqttid phase may come from alloying with the ferrochrome.

Another particularly suitable hinder for preparing the materials of the invention is a mixture of iron and cast iron. The iron is the most economical of the binder materials and the cast iron. because of its low melting point. promotes the liquid phase sintering which occurs in the process of manufacture which will he described in detail hereinafter. Substantially pure iron powders. such as ANCOR MH-l sponge iron powder. manufactured by the Hoeganaes Sponge lron Corporation of Riverton. N.J.. and cast iron powders are commercially availableTTypical screen analyses of available iron and cast iron powder in weight 71 are set forth as follows:

Although either the iron or cast iron powder can be used separately. superior properties are obtained from mixtures of the two; the preferable range of the iron powder being 507! to 90% by weight. It is to be understood. of course. that in the final cemented ferrochrome product. the iron and cast iron will have combined to form a steel. Alternatively. a steel powder can be used directly in place of a mixture of iron and cast iron powders.

The products of the invention are made by a novel powder metallurgy technique which ensures the obtaining of a material having the advantageous properties set forth above. The as-received ferrochrome and metallic binder powders are milled together to provide an intimate mixture of finely divided ferrochrome and binder particles. This can suitably be done in a ball mill and milling should preferably be continued until the particle size of the resulting mixture is such that 90% will pass through a 325 mesh screen. Milling may be continued until 997r of the particles are less than microns in size. Milling will ordinarily be carried out for a period of from 24 to 100 hours depending on equipment used.

The resulting intimate mixture of finely divided powders is then compacted in a mechanical or hydraulic press approximately to the shape of the desired final article under a pressure of 10 to 40 tons/sq. in. This may be accomplished with the aid of a conventional lubricant or organic resin binder. a suitable lubricant comprising about 2 weight71 of paraffin wax. the powders being coated with the lubricant or hinder prior to compacting. if a lubricant or binder is used. it is preferably removed before subjecting the compact to the heating step next to be described.

The compact is heated to a temperature within the range of l850-2400F in an inert or reducing environment achieved by the establishment of vacuum conditions or by provision of a blanket of an inert gas. such as helium. or by use of a reducing gas. such as dissociated ammonia. The binder particles are converted to a totally liquid phase which suhstanti'alkv completely fills all of the voids or spaces between the particles of ferrochrome. As stated above. there may be sintering of ferrochrome particles. but this is not necessary. There re stilts a considerable shrinkage in going from the green compact to the fully sintered part. For fully cemented ferrochrome. there is ordinarily a l5 /r to 187/ linear shrinkage. There results a sintered density of greater than 905' of the theoretical and the material has little or no interconnected porosity.

The sintering stage of the process can ordinarily be completed by heating at the stated temperature for from 15 to l20 minutes.

On cooling. there is obtained a hard. dense material which is suitable for most applications. The articles produced can be subjected to conventional finishing operations to obtain the exact size and finish desired.

However. if a product of particularly great hardncss'is required. hardness can be increased by reheating to a temperature of the order of l.500F in an atmosphere of dissociated ammonia and quenching in oil.

The following examples are set forth as illustrating the invention. but not as limiting the same;

EXAMPLE I The following powders were ball milled in a small steel mill with steel balls for l 12 hours:

40.0 g. ferrochrome 7.5 g. iron 2.5 g. cast iron The milled intimate mixture of powders with a composition of be weight of ferrochrome and 2071 by weight of binder was mixed with an organic resin binder and pelleted into blanks for ball pen balls. The green balls were packed in 60 mesh ZrO and heated slowly to 800F under dissociated ammonia to remove the binder. The crucible was then transferred to a vacuum furnace and the balls sintered at 2.l50F for 30 minutes at 0.2-0.5 torr.

After being ground and finished to size. half of the balls were given a hardening treatment by heating to 1,500F in dissociated ammonia and quenching in oil. Microhardness of the as-sintered balls was DPH 729 and that of the hardened balls was DPH 924. Both types were utilized in ball point pens tested for writing performance and found to be satisfactory. The cemented ferrochrome balls were tested for corrosion resistance as compared to commercial 440C stainless steel ball pen balls by soaking in Super Quink ink at l40F for 48 weeks. The ferrochrome balls were not affected by the test whereas the 440C stainless steel balls were severely attacked and partially disintegrated.

EXAMPLE ll The following powders were ball milled in a steel mill with steel balls for l 12 hours:

80 g. ferrochrome 15 g. iron 5 g. cast iron The resulting mixture of milled powders was mixed with 171 by weight of Carbowax 4000 (Union Carbide Corporation) as a lubricant and pressed into discs approximately A; inch thick in a 0.770 inch diameter cylindrical steel die at a pressure of 10 tons/in The green parts were packed in 60 +100 mesh ZrO and sintered in a vacuum furnace at 2200F for 30 minutes at a pressure of 02 0.5 torr. The sintered parts had shrunk to a diameter of 0.645 inches and had a superficial hard- 5 ness of 15N87. In the final articles. the iron and cast iron had alloyed to provide a steel binder.

The parts showed very little wear and no corrosion when used in the pen nib flexing apparatus as replace ment for chromium plated tool steel wear pads which had chipped and corroded.

EXAMPLE 111 The procedure of Example 11 was used to prepare sintered discs composed of 859 by weight of ferrochrome and 1571 by weight of steel binder. The following amounts of powder were used:

42.500 g. ferrochrome 5.625 g. iron 1.875 g. white cast iron The sintered discs had shrunk to a diameter of 0.65 inches and had a superficial hardness of 15N85.

EXAMPLE IV The following powders were milled in a steel mill with steel balls for 63 hours:

600 g. ferrochrome 300 g. iron 6 following batches of powders in steel mills with steel balls for 100 hours:

A B 800 g. t'erroehrome 800 g. ferrochrome 200 g. white cast iron 200 g. iron C 1) 800 g. I'errochrome 6 g. ferrochrome 100g. iron 175 g, iron I00 g. white cast iron 175 g. white cast iron E 500 g. I'erroehrome 250 g. iron 250 g. white cast iron Samples A B C D F.

Sintcrcd Density g/cc 6.87 6.77 6.91 6.70 6.96 Hardness R.- 56 49 55 40 90R Tensile strength 15 3 I5.1 I3.7 241 483 1000 psi Transverse Rupture 65.2 57.4 89.4 93.5 114.1 Strength 1000 psi Impact Strength 361 4.06 4.35 .16 7.95 ft-lhs/in.

100 g. white cast iron 35 EXAMPLE v The mixture of milled powders was mixed with 2% by weight paraffin wax and compacted at tons/in in a 2 inch diameter cylindrical steel die. The green parts were packed in 60 mesh alumina and sintered by heating slowly to 2,350F under dissociated ammonia in a continuous pusher type furnace and holding this temperature for 1 hour. The sintered parts were finished to size by milling and grinding. Testing of the parts showed the material to be impervious to liquid absorption and to have satisfactory corrosion resistance al though the strength was less than that ofa similar part made from 316L stainless steelpowder.

EXAMPLE V Tensile test bars were prepared from various compositions of ferrochrome. iron and cast iron by milling the A detailed investigation was conducted on the properties of a series of ferrochrome-steel cemented com positions to determine the useful limits of this inven- 0 tion. system. percentage by weight of ferrochrome powder was varied from to 100% with the binder material, except for the 100% ferrochrome composition. being equal weight percentage of iron powder and white cast iron powder. The powders were milled to- 5 gether until the composite powder was essentially less Transverse Rupture Impact *Boiling Sintering Hardness Strength Strength Nitric Acid Composition Atmosphere Rockwell 1000 psi ft-lbs/in. in/month 1571 FeCr" dis. NH R 67 96.7 19.22 0.657 85)? Steel Vac. R 42 137.5 9.45 0.540

% FeCr dis. NIL, R 61 83.0 13.67 0.744 8071 Steel Vac. R,- 38 175.1 9.76 0.229

% FeCr dis. NH R 100 181.3 37.50 0.153 75% Steel Vac. R! 33 147.3 19.84 0.146

35% FeCr dis. NH R 97 143.8 20.36 0.357 659 Steel Vac. R 161 5 18.26 0.182

6071 FeCr dis. NH R,- 41 112.0 4.62 0.072 4071 Steel Vac. R,- 42 117.1 4.85 0.052

'? FcCr dis. NH Rp 58 50.3 6.52 0.027

-continued 'l'ransvcrsc Rupture Impact *lloiling Sintcring Hardness Strength Strength Nitric Acid Composition Atmosphere Rockwell 1000 psi l't-lhs/in." iii/month 20% Steel Vac. R, 56 70.7 8.34 0.009

95"! FcCr" dis. NH R 78 37.9 1.86 0.014 Steel Vac. 11.81 20.1 (1.55 0.010

97% FcCr' dis. NH; R 81 50.9 2.61 0.013 3'? Steel Vac. R 80 21.3 0.67 0.067

99% FcCr dis. NH R. 79 48.8 4.00 0.015 1% Steel Vac. R 82 16.1 0.42 0.017

100' FeCr dis. NH R. 79 44.7 ms 0.04s Vac. R 80 3x8 0.3] 0.016

*ASTM Standard '1 est AIME-5. T

It can be seen that all the compositions have useful properties although for the composites with less than 25 wt.% ferrochrome the corrosion resistance is considerably reduced. Also the properties of the compositions with 95 wt.% and greater amounts of ferrochrome do not change to any great extent. ln interpreting the strength characteristics of these materials it should be noted that these materials fail in a brittle manner and that considerable scatter in test data is to be expected.

The test results show the novel materials of the present invention have properties that are comparable to many commercially available P/M products and that by varying the percentages of the constituents of the compositions it is possible to vary their characteristics over relatively wide limits thereby making them useful for various industrial applications.

EXAMPLE Vll The following powders were ball milled in a small steel mill with steel balls for 72 hours:

25.5 g. ferrochrome powder 4.5 g. nickel alloy powder (60% by weight of nickel, 20% by weight of manganese and 20% by weightof copper) The milled, mixed powder with a composition of 85% by weight of ferrochrome and by weight of binder alloy was processed into ball pen balls in the same man ner as Example 1 except that the final sinter was carried out at 2.300F for 30 minutes under a partial helium pressure of 2.5 torr. The finished balls had a microhardness of DPH 990 and gave satisfactory writing performance when assembled into ball pen points.

EXAMPLE VIII The following powders were milled for 112 hours:

40 g. ferrochrome 10 g. Monel (70% by weight of nickel and 30% by weight of copper) The mixture of milled powders with a composition of 80% by weight of ferrochrome and by weight binder alloy was processed into balls as described in Example 1. The balls had a microhardness of DPH 603 and gave satisfactory writing performance in ball pen points.

EXAMPLE lX The following powders were milled for 112 hours:

13.6 g. ferrochrome 3.4 g. cobalt alloy (50% by weight of cobalt, 30% by weight of nickel and 20% by weight of chromium) The mixture of milled powders with a composition of 80% by weight of ferrochrome and 20% by weight of binder alloy was processed into balls which had a microhardness of DPH 724 and gave satisfactory writing performance in ball pen points.

EXAMPLE X EXAMPLE Xl An experiment was conducted using silver as the binder metal for ferrochrome. The powdered metals in ratios to give 10%, 20% and 3.0% by weight silver composites were mixed together in a mortar, compacted in a 0.25 inch diameter cylindrical steel die at 20 tons/in, and sintered in a vacuum furnace at 1.850F for 30 minutes at l torr. pressure of helium. There was little or no shrinkage of the compact but metallographic examination indicates good wetting of the ferrochrome particles by the silver.

EXAMPLE Xll The experiment of Example Xl was repeated except that palladium powder was added to prepare a composition of 80% by wieght of ferrochrome, 16% by weight of silver and 4% by weight of palladium. Sintering at 2.200F resulted in a compact with a good strength but little shrinkage.

EXAMPLE Xlll The experiment of Example Xl was repeated except that a prealloyed powder of by weight of silver, 20% by weight ofpalladium and 10% by weight ofmanganese was used as the binder metal to prepare a composition of 70% by weight of ferrochrome and 30% by weight of the silver-palladium-manganese alloy. Sintering at 2.350F for 15 minutes at 200 torr. helium pressure resulted in shrinkage from 0.250 inches to 0.240

9 inches in diameter. The part had good strength and a hardness value of 30N-75.

There has thus been described the making of cemented ferrochrome materials which are hard. dense. highly impermeable. corrosion resistant and of good strength. The materials have a low coci'ticient of thermal expansion. generally of the order of microinch/inch/F.

The materials of the invention can be used. in general. for any of the applications for which stainless steel parts formed by powder metallurgy techniques from stainless steel powders have been used. The present materials are particularly suited for the manufacture of ball point pen balls.

I claim:

1. A cemented ferrochrome material comprising a composite mass of from to 95% by weight of finely divided terrochrome particles adhered by from 5% to 75% by weight of a metallic binder having a meltin point below that of said t'errochrome.

2. A material as claimed in claim 1 in which 90% of said ferrochrome particles are of a size less than 325 mesh.

3. A material as claimed in claim 3 in which 99% of said ferrochrome particles are ofa size less than 20 microns.

4. A material as claimed in claim 1 in which said metallic binder is selected from the group consisting of iron, nickel. cobalt. chromium. manganese. copper. silver. palladium and their alloys.

5. A material as claimed in claim 4 in which said metallic binder also contains platinum.

6. A material as claimed in claim 1 in which said metallic binder is selected from the group consisting of iron. cast iron. steel. silver. an alloy of nickel and copper. an alloy of nickel. manganese and copper. an alloy of cobalt. nickel and chromium. an alloy of silver and palladium. an alloy ofsilver. palladium and manganese, an alloy of cobalt. nickel. chromium. iron, and platinum. and an alloy of cobalt. nickel. chromium. and platinum.

7. A material claimed in claim 1 in which said metallic binder contains cobalt and nickel and. by weight about 18 to 20% chromium, 0.1 to 1% platinum and 0 to 3% iron.

8. The material of claim 7 wherein the binder alloy contains. by weight. about to 60% cobalt and 20 to nickel.

9. The material of claim 7 wherein the binder alloy contains. by weight, about 45 to cobalt and 25 to 35% nickel.

10. The material of claim 7 wherein the binder alloy contains. by weight. 0% iron.

11. A material as claimed in claim 2 in which said ferrochrome particles are composed of a high carbon ferrochrome containing about by weight of chromium. about 25% by weight of iron and about 5% by weight of carbon.

12. A cemented ferrochrome material comprising a composite substantially impermeable mass of from 25% to 95% by weight of finely divided ferrochrome particles adhered by from 5% to by weight of a metallic binder having a melting point below that of said ferrochrome.

13. A material as claimed in claim 12 in which of said ferrochrome particles are of a size less than 325 mesh.

14. A material as claimed in claim 13 in which 99% of said ferrochrome particles are of a size less than 20 microns.

15. A material as claimed in claim 12 in which said metallic binder is selected from the group consisting of iron. nickel. cobalt. chromium. manganese. copper. silver, palladium and their alloys.

16. A material as claimed in claim 15 in which said metallic binder also contains platinum.

17. A material as claimed in claim 12 in which said metallic binder is selected from the group consisting of iron, cast iron. steel, silver. an alloy nickel and copper. an alloy of nickel. manganese and copper. an alloy of cobalt, nickel and chromium. an alloy of silver and palladium, an alloy of silver. palladium and manganese. an alloy of cobalt. nickel. chromium. iron. and platinum. and an alloy of cobalt, nickel. chromium, and platinum.

18. A material as claimed in claim 12 in which said metallic binder contains cobalt and nickel and. by weight. about l8 to 20% chromium. 0.1 to l% platinum and 0 to 3% iron.

19. The material of claim 18 wherein the binder alloy contains. by weight. about 30 to 60% cobalt and 20 to 50% nickel.

20. The material of claim 18 wherein the binder alloy contains, by weight. about 45 to 55% cobalt and 25 to 35% nickel.

21. The material of claim 18 wherein the binder alloy contains, by weight, 0% iron.

22. A material as claimed in claim 13 in which said ferrochrome particles are composed of a high carbon ferrochrome containing about 70% by weight of chromium, about 25% by weight of iron. and about 5% by weight of carbon. 

1. A CEMENTED FERROCHROME MATERIAL COMPRISING A COMPOSITE MASS OF FROM 25% TO 95% BY WEIGHT OF FINELY DIVIDED FERROCHROME PARTICLES ADHERED BY FROM 5% TO 75% BY WEIGHT OF A METALLIC BINDER HAVING A MELTING POINT BELOW THAT OF SAID FERROCHROME.
 2. A material as claimed in claim 1 in which 90% of said ferrochrome particles are of a size less than 325 mesh.
 3. A material as claimed in claim 3 in which 99% of said ferrochrome particles are of a size less than 20 microns.
 4. A material as claimed in claim 1 in which said metallic binder is selected from the group consisting of iron, nickel, cobalt, chromium, manganese, copper, silver, palladium and their alloys.
 5. A material as claimed in claim 4 in which said metallic binder also contains platinum.
 6. A material as claimed in claim 1 in which said metallic binder is selected from the group consisting of iron, cast iron, steel, silver, an alloy of nickel and copper, an alloy of nickel, manganese and copper, an alloy of cobalt, nickel and chromium, an alloy of silver and palladium, an alloy of silver, palladium and manganese, an alloy of cobalt, nickel, chromium, iron, and platinum, and an alloy of cobalt, nickel, chromium, and platinum.
 7. A material as claimed in claim 1 in which said metallic binder contains cobalt and nickel and, by weight about 18 to 20% chromium, 0.1 to 1% platinum and 0 to 3% iron.
 8. The material of claim 7 wherein the binder alloy contains, by weight, about 30 to 60% cobalt and 20 to 50% nickel.
 9. The material of claim 7 wherein the binder alloy contains, by weight, about 45 to 55% cobalt and 25 to 35% nickel.
 10. The material of claim 7 wherein the binder alloy contains, by weight, 0% iron.
 11. A material as claimed in claim 2 in which said ferrochrome particles are composed of a high carbon ferrochrome containing about 70% by weight of chromium, about 25% by weight of iron and about 5% by weight of carboN.
 12. A cemented ferrochrome material comprising a composite substantially impermeable mass of from 25% to 95% by weight of finely divided ferrochrome particles adhered by from 5% to 75% by weight of a metallic binder having a melting point below that of said ferrochrome.
 13. A MATERIAL AS CLIAIMED IN CLAIN 12 IN WHICH 90% OF SAID FERROCHROME PARTICLES ARE OF A SIZE LESS THAT 325 MESH.
 14. A material as claimed in claim 13 in which 99% of said ferrochrome particles are of a size less than 20 microns.
 15. A material as claimed in claim 12 in which said metallic binder is selected from the group consisting of iron, nickel, cobalt, chromium, manganese, copper, silver, palladium and their alloys.
 16. A material as claimed in claim 15 in which said metallic binder also contains platinum.
 17. A material as claimed in claim 12 in which said metallic binder is selected from the group consisting of iron, cast iron, steel, silver, an alloy nickel and copper, an alloy of nickel, manganese and copper, an alloy of cobalt, nickel and chromium, an alloy of silver and palladium, an alloy of silver, palladium and manganese, an alloy of cobalt, nickel, chromium, iron, and platinum, and an alloy of cobalt, nickel, chromium, and platinum.
 18. A material as claimed in claim 12 in which said metallic binder contains cobalt and nickel and, by weight, about 18 to 20% chromium, 0.1 to 1% platinum and 0 to 3% iron.
 19. The material of claim 18 wherein the binder alloy contains, by weight, about 30 to 60% cobalt and 20 to 50% nickel.
 20. The material of claim 18 wherein the binder alloy contains, by weight, about 45 to 55% cobalt and 25 to 35% nickel.
 21. The material of claim 18 wherein the binder alloy contains, by weight, 0% iron.
 22. A material as claimed in claim 13 in which said ferrochrome particles are composed of a high carbon ferrochrome containing about 70% by weight of chromium, about 25% by weight of iron, and about 5% by weight of carbon. 